(1) Field of the Invention
The present invention relates to a solid-state imaging device, and in particular, to a solid-state imaging device that can reduce the number of types of electric power and the number of electric terminals.
(2) Description of the Related Art
In general, a charge-coupled device (CCD) solid-state imaging device is used for the solid-state imaging device that composes an imaging device installed in a camera, especially a digital still camera.
FIG. 1 is a schematic diagram showing a top view of a conventional CCD solid-state imaging device (e.g., see reference to Japanese Patent No. 3313125, pp. 1-3 and FIG. 15).
As shown in FIG. 1, the conventional solid-state imaging device has a structure in which an imaging unit 900 for imaging an object, and a peripheral circuit portion 910 are formed in a main surface portion of a semiconductor substrate 920 formed in a chip.
The imaging unit 900 includes, though not shown in the diagram, photodiodes, vertical CCDs, horizontal CCDs and an output amplifier. The imaging unit 900 transfers signal charge generated by performing photoelectric conversion on incident light, converts the signal charge into an electric signal, and outputs the electric signal as an image signal.
The peripheral circuit portion 910 includes: nine signal electrode pads 911 for inputting and outputting signals; two power supply electrode pads 912 for supplying power; a protection circuit 913 for protecting the imaging unit 900 from static electricity that comes in from the exterior; and an electrostatic electrode pad 914 for discharging such static electricity.
The signal electrode pad 911 includes the following electrode pads: an electrode pad to which four-phase pulses of V1, V2, V3 and V4 for driving the vertical CCDs are provided; an electrode pad to which two-phase pulses H1 and H2 for driving the horizontal CCDs are provided; an electrode pad to which a pulse RG, which resets a floating diffusion layer to which signal charge is transmitted from the horizontal CCDs, is provided; and an electrode pad to which a pulse SUB, which sets an overflow barrier for discharging an excess of charge generated in the photodiodes and realizes electronic shutter operation for forcibly discharging the signal charge in the photodiodes, is provided; and an electrode pad for outputting an image signal from the output amplifier.
The power supply electrode pad 912 consists of the following: an electrode pad to which a power voltage Vod such that provided to the output amplifier is provided; and an electrode pad to which a reference voltage Vwell is provided.
A voltage Vss with the level as low as a low level voltage of the pulse V1, V2, V3 or V4 is provided from outside to the electrostatic electrode pad 914.
The protection circuit 913 includes a diode whose anode is connected to the electrostatic electrode pad 914 and whose cathode is connected to any one of the signal electrode pads 911. Such protection circuit 913 discharges, to the electrostatic electrode pad 914, the static electricity that has come into the signal electrode pad 911 from the exterior, and thus protects the imaging unit 900. For example, the protection circuit 913, which is connected to the signal electrode pad 911 to which the pulses V1 to V4 are provided, discharges the static electricity that has come into the signal electrode pad 911 to which the pulses V1 to V4 are provided, and protects a driving electrode in the vertical CCD.